Dual finishing wheel



March 30, 1954 R KARNELL 2,673,425

DUAL FINISHING WHEEL Filed May 20, 1953 INVENTOR. ROLAND D. KARNELL ATTORNEY Patented Mar. 30, 1954 UNITED STATES PATENT OFFICE This invention relates to a dual tool finishing wheel. More specifically, the invention relates to a dual wheel having a finish grinding portion and a lap cutting portion mounted on a single rotary shaft.

Considerable difficulty has .been encountered previously in sharpening single point tungsten carbide cutting tools without the use of diamond wheels. It is also desirable to hav a high finish around the cutting edges of such tools to improve their cutting ability and increase their life.

The present invention provides a dual finishing Wheel which is provided with an outer cuptype grinding wheel, such as a bonded silicon carbide wheel and an inner rotary diamond lapping wheel, both adapted to be mounted on a single rotary shaft so as to be instantly available for use as desired in finishing cutting tools.

Further details and advantages of my invention will be apparent from the following specification and appended drawings, wherein Figure 1 is an exploded perspective view of the component parts of my dual finishing wheel, and

Figure 2 is a transverse sectional axial view of the assembled dual finishing wheel.

Referring to the drawings, the dual finishing wheel consists of an outer cup-type grinding wheel I0, mounted on a circular backing plate I I, having a central opening I2 and spaced bolt receiving openings I3 for mounting the plate on a suitable rotary spind1e mount of a tool grinder in the usual way. The grinding wheel I is preferably made of silicon carbide, vitrified bonded or resinoid bonded, having a grit size ranging from about 60 to about 180. It may also be made of aluminum oxide or other suitabl abrasive material.

The hollowed cup portion of the grinding wheel is adapted to snugly receive a circular auxiliary insert plate I 4 provided with a plurality of spaced bolt receiving openings I5 which are adapted to mate with the openings I3 in plate I I for securing same to the spindle mount of a tool grinder. The insert plate I4 is also provided with an extending hub or bearing portion I6 terminating in a threaded post IT. The insert plate I4 is adapted to support an inner lap cutting wheel I 8 as shown in Figure 2 and is retained in place by means of washer I9, lock washer and nut 2I mounted on threaded post I1 as shown in Figure 2. This assembly is thus adapted to rotate as a unit when suitably mounted on the spindle mount of a rotary tool grinder.

The rotary lap wheel I8 is preferably made of molded laminated paper bonded with a suitable phenolic resin. The lap wheel I8 is provided with a bore IBe having a flat seat I89 at the bottom thereof for supporting washer I9 thereon as shown in Figure 2. The lap wheel I8 is also provided with an axial bore I8) which is adapted to snugly receive the hub I 6 of insert plate. The rear face I of wheel I8 is a1so provided with an offset portion I 8b which is adapted to be supported on insert plate I4 as shown in Figure 2. The offset portion I8b provide a sumcient space between the auxiliary insert plate I4 and the face IBc of the lap wheel IBto receive the heads of fastening bolts positioned in holes I5 of plate I4. It will also benoted that the cup-type inner surface IIlbof the grinding wheel I0 is spaced a short distance ,a from the outer surface I3cl of the lap wheel I8 as shown in Figure 2 for a purpose to be explained later.

In using the assembled dual finishing wheel as described to finish a tungsten carbide single point tool, the tool is first ground dry on the grinding wheel I0 by bringing the desired tool surface against the lateral surface Ifla of wheel III. The surface Illa of wh l I0 is preferably dressed back and trued so as to allow the lateral surface I8a of the inner lap wheel I8 to extend out or forward a distance b of at least 1% to 4; inch. The distance a between the inner surface lb of grinding wheel I0 and the surface I8d of the lap wheel I8 should preferably be at least about 4; inch so as to permit dressingof the entire lateral surface Illa of grinding wheel II). If desired th grinding wheel I0 may be dressed with a suitable sharp diamond dressing tool to prepare the surface thereof. The tool to be finished is first finish ground on the grinding wheel III. This ground tool is then finished by bringing the desired surfaces thereof in contact with lateral surface I8a of the lap wheel I8 so as to produce the desired finish. Before doing this the surface I8a is coated or charged with a suitable diamond paste which is first spread with a finger and then rolled into the surface of the lap wheel with a suitable metal roller under suitable pressure. The grit size of diamond paste applied depends upon the type of cutting action or finish desired as given in the following table:

Grit Size (Mesh E quivalent) Particle ze (Microns) Results of Cutting Action Very Coarse. Extra Coarse. Coarse. Medium Coarse. Medium Cut.

0 Light Cut.

Medium Micro. Light Micro. Fine icro.

In utilizing the procedur as described it is possible to produce a mirror finish on the surfaces of tungsten carbide cutting tools. The life of such tools can be extended as much as three or more times that of the same carbide tools having a conventional finish. Measurements with a profilometer show that this finishing refines the surfacesf-rom a range of 15 to 20 R. M. S.. mu in., produced with conventional grinding, to 1 to 2 R. M. S. mu in., when finish-lapped with a U. S. Standard #30 or 600 grit equivalent diamond grit size. The effect on the cutting edge is a. reduction from around 30 R. M. S. mu in. with conventional grinding, to as little as '8' R. S. -mu in. after refined finishing.

My dual finishing wheel makes it possible "to achieve the aforementioned results with aminimum of time and effort because both the grinding wheel and lap wheel are instantly available on a single rotary shaft for the necessary finishing operations.

It is to be understood that modifications and changes may be made in the specific details of the construction of the dual finishing wheel which are intended to be included within the scope of the appended claims.

I claim:

1. A dual finishing wheel comprising an outer cup-type grinding wheel and an inner lap wheel retained within the cup portion of said outer grinding wheel, wherein the outer cup-type grinding wheel is, made of silicon carbide and the inner lap wheel is made of laminated paper bonded, with a. phenolic resin, said lap wheel being, charged with. diamond paste for finishing ac ion.

received om-said hub and provided with a seat for supporting a locking washer and nut and a recessed portion in the rear face thereof for receiving the heads of bolts fastening same to the said auxiliary plate.

V ROLAND D. KARNELL.

References Cited in the fileof this patent UNITED STATES PATENTS Number Name Date:

831,541 Davis Sept. '25-,- 1906 1,364,625 Eriksen Jan. 4', 1921 1,963,394 Yassenoff June 19, 1 93141 1,984,205 Vinella Dec. 11,1934 2,282,096 Talboys -1 May 5, 1 942 2,660,840 Bergstrom Dec. '1, 1953 FOREIGN PATENTS Number Country Date 98,606 Germany Sept. 19, 1897 199,312 Germany Nov. 10, 1-907 

